1. Technical Field
The present invention generally relates to a pump system or other rotational equipment; and more particularly to a pump system or other rotational equipment having a module or other suitable device for performing pump condition monitoring.
2. Description of Related Problem
There are several commonly employed techniques to obtain the rotational speed of a pump or other rotating equipment:
For example, a photo tachometer directs either a laser, infer red or visible light toward a reflective tape attached on the rotating shaft of a pump or other rotating equipment. A photo pickup in the photo tachometer senses the change in reflected light each time the tape passes. Speed in revolutions per minute is calculated from the period between the sensed light intensity changes.
An inductive or capacitive switch may be placed near the key or keyway or the rotating shaft of the pump or other rotating equipment. As the key or keyway moves past the switch, it causes a change of state of the switch. Again an indicator connected to the switch measures the period between change of states of the switch and calculates the speed in revolutions per second or per minute.
A sixty tooth gear may be attached to some section of the shaft of the pump or other rotating equipment. Placed near to the gear is an electromagnetic sensor that is capable of generating a voltage dependent on the proximity of metal to it. The time varying voltage signal is connected to a frequency counter. Because a 60 tooth gear is used, the frequency (hertz) counter displays speed directly in revolutions per minute.
A vibration sensor on the pump or other rotating equipment connected to a spectrum analyzer with sufficient frequency resolution can indicate the frequency of 1× vibrations of the equipment.
An older but still used way of determining the operating speed of a pump or other rotation equipment is to use a strobe light. The strobe light is pointed to the part of the rotating shaft and the strobe's flashing rate is adjusted until the shaft appears to stop rotating. The strobe's flashing rate can be the actual operating speed of the equipment.
Moreover, a magnet collar may be attached to the rotating shaft with a Hall effect sensor positioned nearby. Such is the technique employed in patent application Ser. No. 10/142,181, filed on 9 May 2002, entitled “Self contained Pump Electrical Equipment Power supply”, which is incorporated by reference herein in its entirety. However, when attempting to measure speed using the self contained pump electrical equipment power supply device described therein, a Hall Effect sensor was embedded in the stator of the generating device and wired back to an indicator circuit. As the magnets rotated past the Hall Effect sensor, it would change state and the period of the state changes along with the number of magnets past the Hall Effect sensor per revolution were used to calculate the rotational speed of the shaft.
All of the above methods are valid techniques for obtaining the speed of a rotating piece of equipment. All have and are being employed in the art. The disadvantage for all of the above systems is that they require a sensing device and the wiring back to an indicator. The whole thrust of the present invention is to eliminate such a sensing device.
Moreover, a patentability search was conducted on the present invention and various patents were developed in the search, which are summarized as follows:
One patent discloses a solid state pump control and protection system having a power supply coupled to a pump control system for controlling the operation of a pump. The pump control system has an analog module with a current phase detector, a pressure transducer and an over/under voltage detector, for analyzing the status of the pump based on these sensed parameters. A second patent discloses a variable speed induction motor control system having a DC bridge that has its input coupled to a source of 60 Hz three phase power. This input is not directed, before being rectified, to any circuit, especially a zero crossing circuit. The DC bridge is also coupled to a Hall Effect sensor for detecting the current from the same. A third patent discloses a variable RPM submersible pump that may be controlled by a variable drive system, having a rectifier that receives inputs from a three phase power source located at the surface. Similar, to that disclosed in the above patents, no input from the three phase power source is directed, before being rectified, to any circuit, especially a zero crossing circuit. A fourth patent discloses a pump protection module or device having two input nodes for coupling to an AC power source and a motor M, which includes a voltage filter and zero-cross detection circuit and a current filter and zero-cross detection circuit both coupled to a microcontroller. In operation, the microcontroller opens and closes the switch based on a phase comparison between the voltage and current signals from these circuits depending on a determined load condition. Similar, to the above patents, the microcontroller does not use the input from these circuits to obtain the rotational speed of a pump or other suitable rotating equipment. None of these patents developed in the search disclose the whole thrust of the present invention.